Installing one or more skylights in a wall of a trailer of a semi-tractor trailer truck may improve visibility in the interior of the trailer making it easier for the driver and others to navigate the interior of the trailer and to view, load, and unload the freight being carried. Installation may be done on an after-market basis by purchasing skylight assembly installation kits. Making installation easy while at the same time ensuring that the skylights are well sealed from the elements to prevent precipitation, among other things, from entering the trailer are important factors. The prior art solutions have not adequately addressed both of these factors and there is therefore a need for an improved skylight.